Abstract:

Mesocosm experiments were performed with Gulf of Mexico seawater collected 8 km offshore south of Galveston, Texas and were amended with microbial concentrate. The three treatments in triplicate were analyzed for oil composition were 1) Control, 2) Water accommodated oil fraction (WAF), and 3) diluted chemically enhanced (Corexit) WAF (DCEWAF). The oil composition data presented here are estimated oil equivalence (EOE) using fluorescence, polycyclic aromatic hydrocarbon (PAH), total PAH and biomarkers. Additionally, the total and dissolved nutrients for these treatments are also included.

Suggested Citation:

Gopal Bera, Maya Erin Morales-McDevitt, Terry Wade, Tony Knap. 2019. Oil concentration, oil composition, biomarkers, and nutrients for the mesocosm LTMOSE, a Long Term Marine Oil Snow Experiment. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-hs2n-xf29

Publications:

Shi, D., Bera, G., Knap, A. H., Quigg, A., Al Atwah, I., Gold-Bouchot, G., & Wade, T. L. (2020). A mesocosm experiment to determine half-lives of individual hydrocarbons in simulated oil spill scenarios with and without the dispersant, Corexit. Marine Pollution Bulletin, 151, 110804. doi:10.1016/j.marpolbul.2019.110804

Purpose:

To determine the concentration of oil and dispersant and their degradation with time in three different mesocosm treatments from seawater. Also, to track the change in nutrients during the same time course.

Data Parameters and Units:

DN M5.csv: Sample ID; Collection date (DD/MM/YYYY); Concentrations of nitrate (NO3-), hydrogen phosphate (HPO4), hydrogen silicate (HSIO3-), ammonium (NH4+), nitrite (NO2-), and urea in Mesocosm 5 in umol/L and mg/L with respect to the listed standard; Concentration of nitrate + nitrite (NO3-+NO2-) in uM. EOE M5 GRIIDC.csv: Time (hour); Sample ID; concentrations of WAF and DCEWAF in mg/L. M5 alkanes GRIIDC-1 TLW.csv: Treatments at three different time points (T0, T72 and T360 hours); Sample ID; Sample volume (L); concentrations of several alkanes (n-C10-35) and the total concentration of alkanes in mesocosm treatments in ng/L; total resolved alkanes, total petroleum hydrocarbon (TPH) and total unresolved complex mixture (UCM) in relation to the resolved alkanes in ug/L. M5 PAHs GRIIDC-TLW.csv: Treatments at three different time points (T0, T72 and T360 hours); Sample ID; Sample volume (L); concentrations of polycyclic aromatic hydrocarbon (PAH) compounds in ng/L. TN M5.csv: Client ID; Collection date (DD/MM/YYYY); Concentrations of total Nitrogen (Total N), total phosphorus (Total P) in umol/L and mg/L, and hydrogen phosphate (HPO4) concentration in umol/L with respect to the listed standard. Note: EOE = Estimated Oil Equivalence; M5 = Mesocosm 5, C = Control, O = WAF, M = CEWAF; DM = DCEWAF, A = replicate "A", B = replicate "B", C = replicate "C", D = replicate "D", E = replicate "E", F = replicate "F"; CA, CB, CC, CD, CE, CF = Control replicates; OA, OB, OC, OD, OE, OF = WAF replicates; DMA, DMB, DMC, DMD, DME, DMF = DCEWAF replicates. -999 = below detection limit.

Methods:

M5: Mesocosm method for LTMOSE, a Long Term Marine Oil Snow Experiment Eighteen 110L capacity glass mesocosm tanks were filled with Gulf of Mexico seawater collected 8 km offshore south of Galveston, Texas that had been pre-treated with a charcoal filter to remove large particles and debris. The salinity was 25 PSU. Plankton (≥63 µm) were collected using a net and transferred into polycarbonate bottles after being prefiltered (115 um) to remove zooplankton, jellyfish and debris. Six replicates mesocosms for each of the three treatments (Control, WAF and DCEWAF) were prepared. The goal was to start the experiment with approximately the same concentration of oil in the WAF as the DCEWAF, i.e., a target concentration of 2mg/L. The water accommodated fraction (WAF) of oil was prepared by mixing 25 mL (5 ml ~ 5 min over 25 min) of Macondo surrogate oil into six baffled recirculating tanks (Wade et al., submitted) containing ~130 L of seawater were mixed vigorously for 4 hrs to create a “high energy” WAF (Knap et al., 1983). The WAF was then introduced into the WAF mesocosm tanks, filled to 104L, and mixed. From these tanks, 3.5 L WAF was removed for hydrocarbon analyses. Corexit was mixed with oil in a ratio of 1:20 to make diluted chemically enhanced water accommodated fraction (DCEWAF). Then 25 mL of this mixture (5 ml every 5 min for 25 min) of surrogate oil plus Corexit was added to a baffled recirculating tank containing ~130 L of seawater which was not vigorously mixed for 4 hrs prior to being loaded into the mesocosm tanks. From these CEWAF tanks, 5L was removed for other analyses (3.5 L hydrocarbon analyses). Diluted CEWAF (DCEWAF) was prepared by mixing 10.4 L of CEWAF with 93.6 L of the original seawater for a total volume of 104 L. This concentrated plankton mass was introduced to each of the tanks (1.5 L to each tank which contained 104L of treated seawater, total volume of seawater 105.5L per tank) immediately prior to starting the experiments. Banks of lights were placed behind each of the glass mesocosm tanks and a 12:12 light/dark cycle employed. The first three control and WAF mesocosms were sampled day 1 and sacrificed day 4 for a quantitative marine snow collection. The second set of triplicate Control and WAF mesocosms were sampled day 8 and scarified day 16 for a quantitative marine snow collection. Days 1 and 8 only surrounding seawater samples were collected through a 5 cm diameter Teflon faucet, positioned 10 cm from the bottom of each mesocosm. Days 4 and 16 the whole tank was sacrificed after collection of surrounding seawater, to quantitatively sample all sunken marine snow. From these DCEWAF tanks, 5L was removed for other analyses (4 L hydrocarbon analyses). The estimated oil equivalents (EOE) were determined using Macondo surrogate oil as the calibration standard (Wade et al., 2011) for the fluorescence analyses (Horiba Scientific Aqualog Fluorometer). The EOE mean concentration of the six treatments for the control, WAF and DCEWAF at the start of the experiments were below detection (0.05), 2.15, and 2.62 mg/L, respectively very close to the target concentrations. Hydrocarbon extraction from water was according to Wade et al., 2017.

Instruments:

An Agilent 6890 gas chromatograph with a mass selective detector was used measure PAH concentrations while an Agilent 5890gas chromatograph with a flame ionization detector was used to measure TPH (total petroleum hydrocarbon).

Provenance and Historical References:

Knap, A. H., Sleeter, T. D., Dodge, R. E., Wyers, S. C., Frith, H. R., & Smith, S. R. (1983). The effects of oil spills and dispersant use on corals. Oil and Petrochemical Pollution, 1(3), 157–169. doi:10.1016/s0143-7127(83)90134-5 Wade, T.L., Sweet, S.T., Sericano, J.L., Guinasso, N.L., Diercks, A.R., Highsmith, R.C., Asper, V.L., Joung, D., Shiller, A.M., Lohrenz, S.E. and Joye, S.B. (2011). Analyses of Water Samples From the Deepwater Horizon Oil Spill: Documentation of the Subsurface Plume. Geophysical Monograph Series, 77–82. doi:10.1029/2011gm001103 Wade, T. L., Morales-McDevitt, M., Bera, G., Shi, D., Sweet, S., Wang, B., et al. (2017). A method for the production of large volumes of WAF and CEWAF for dosing mesocosms to understand marine oil snow formation. Heliyon, 3(10), e00419. doi:10.1016/j.heliyon.2017.e00419

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